This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The main study will evaluate whether the investigational drug Creatine is able to slow the progression of Parkinson's Disease (PD). The research hypothesis is that the group being treated with Creatine will show less disease progression by 5 years than the group on placebo as evaluated by a Global Statistical Test comprised of generally measured PD functioning: ambulatory capacity, cognitive impairment, and global functioning. Secondary specific aims are to compare the Creatine and placebo groups on additional measures of efficacy, safety, and tolerability using data between baseline and 5 years follow up. Within the NET-PD LS-1 a sub-study is being conducted for blood sample collection to obtain and store DNA for future PD/and neurological disease research. The blood collection for DNA sampling is a one time blood draw taking at the screening/baseline visit of consenting participants. Procedures involving human subjects will be conducted during clinical visit of which there will be at least 9 during the 5 year study. After the second year there will be at least three telephone contacts to review side effects, medications, health provider visits, and a study medication questionnaire. The most extensive clinical will comprise of the following: Personal and Family Medical History, Vital Signs (pulse, blood pressure, weight), Activities of Daily Living, Overall Functioning Questionnaire, Thinking Ability Test, Memory Test, Depression Scale (Beck Depression Inventory), Blood and urine testing (1 Tbs. of blood will be collected for routine testing), Pregnancy test for qualifying individuals, Parkinson's exam, and ECG will be performed at three visits on a subset of enrolled participants. In addition to the clinical procedures, questionnaires performed during telephone calls will again be administered during visits to the clinic.